From propargylic biscarbonate to diaryl[n]dendralenes

An efficient cross-coupling reaction using a low cost carbon-supported palladium (Pd/C) catalyst for the synthesis of cross-conjugated compounds, diaryl[n]dendralenes, has been developed. The reaction of a propargylic biscarbonate with phenylboronic acid using Pd/C and phosphine ligand (S-Phos) gave 2,3-diphenyl[2]dendralene in high yield. We found that Pd/C was an effective catalyst for the synthesis of dialyl[n]dendralenes. The synthesis of various dendralenes was successfully achieved under the optimized conditions, giving dialyl [2] and [4] dendralenes in good yields.     

Henry reaction catalyzed by copper(I) complexes of a new pyridine‐containing macrocyclic ligand

The synthesis and characterization of copper(I) complexes of the novel pyridine‐containing macrocyclic ligand (PC‐L) and their use as catalysts in the Henry reaction are reported. The pyridine‐based 12‐membered tetraaza macrocyclic (PC‐L) ligand 1 can be obtained in good overall yield (85%) from commercially available starting materials. The Cu(I) complexes showed good catalytic activities in the Henry reaction of different aldehydes and nitroalkanes. Remarkable diastereoselectivity was observed when isatine was reacted with nitroethane under catalytic conditions. Copyright © 2011 John Wiley & Sons, Ltd.     

Efficient and diversity-oriented total synthesis of Riccardin C and application to develop novel macrolactam derivatives

Riccardin C (RC, 1) is a macrocyclic bis(bibenzyl) natural product exhibiting remarkable biological activity as a nuclear liver X receptors (LXRs) ligand and a lipid metabolism mediator. RC is expected to be a lead compound to develop drugs for atherosclerotic diseases, and therefore exploiting diversity-oriented synthesis of RC is a promising approach to drug discovery. In this paper, we report novel total synthesis of RC (7.4% overall yield in 16 steps) by using the intramolecular S_NAr reaction as key cyclization reaction. This is the first example of efficient macrocyclization using 3-nitro-4-fluorostilbene as an electrophile. The methodology could be applied to synthesize novel lactam analogs of RC. The diversity-oriented synthesis of RC is versatile method for the synthesis of various types of bis(bibenzyl) natural products and their derivatization.     

Enantioselective total synthesis of (S)-(+)-lennoxamine through asymmetric hydrogenation mediated by l-proline-tetrazole ruthenium catalyst

A novel asymmetric synthetic strategy to prepare isoindolobenzazepine based lennoxamine alkaloid has been achieved in high ee% starting from 2-(benzo[d][1,3]dioxol-5-yl)ethanamine and 1-(chloromethyl)-2,3-dimethoxybenzene in 5 steps and with a 34% overall yield. The potentiality of this route involved the Bischler-Napieralsky cyclization that leads to tetracyclic indolinium skeleton, generation of chiral center through asymmetric hydrogen-transfer reaction employing l-proline-tetrazole as chiral ligand with Ru/Ir/Rh, and anodic oxidation as the key steps in the synthesis.     

Terephthalic acid derived ligand‐stabilized palladium nanocomposite catalyst for Heck coupling reaction: without surface‐modified heterogeneous catalyst

A new protocol is reported for the synthesis of a heterogeneous palladium nanocomposite stabilized with a terephthalic acid‐derived ligand (N ,N ‐bis(4‐hydroxy‐3‐methoxybenzylidene)terephthalohydrazide). This is a highly insoluble ligand in common organic solvents, except dimethylformamide and dimethylsulfoxide. The resulting palladium nanocomposite acts as an efficient catalyst precursor for Mizoroki–Heck coupling reactions conducted under various reaction conditions. The spectral data suggest that the rate, yield and recycling of the catalyst are more effective for C–C coupling reactions. Copyright © 2016 John Wiley & Sons, Ltd.     

Low-Temperature Template Synthesis of [4,6,6-Trimethyl-2,6-dithioxo-3,7-diazanon-4-enebis(imidothioato)]copper(II) in Gelatin-Immobilized Cu2[Fe(CN)6] Matrix Materials

Complexation in gelatin-immobilized copper(II) hexacyanoferrate(II) matrices on contact withalkaline (pH 10) aqueous solutions containing dithiooxamide, acetone was studied. Under these conditions'template synthesis occurs to give the chelate CuL [L is 4,6,6-trimethyl-2,6-dithioxo-3,7-diazanon-4-enebis-(imidothioato) ligand], with dithiooxamide and acetone acting as ligand synthons. The reaction pattern was suggested. Attempted reaction of dithiooxamide and acetone in solution in the absence of Cu(II) does not yield this ligand.     

Construction of Chiral 2,3‐Allenols through a Copper(I)‐Catalyzed Asymmetric Direct Alkynylogous Aldol Reaction

Chiral 2,3‐allenols were constructed through copper(I)‐catalyzed asymmetric direct alkynylogous aldol reaction. With aromatic and heteroaromatic aldehydes, the alkynylogous aldol reaction with (R)‐DTBM‐SEGPHOS as the ligand proceeded smoothly to furnish the products in excellent regioselectivity with good to high diastereoselectivity and excellent enantioselectivity. In the cases of aliphatic aldehydes, esters of but‐2‐yn‐1‐ol as the substrates and (R,R)‐Ph‐BPE as the ligand were found to be crucial to get good to high regio‐ and diastereoselectivity. The produced chiral 2,3‐allenols are easily transformed into synthetically useful 2‐furanones through cyclization. Finally, the developed method was successfully applied in the rapid synthesis of two chiral intermediates toward the synthesis of two pharmaceutically active compounds that have been proposed for the treatment of neurological disorders.     

3,5-二(2-吡啶基)吡唑的合成方法改进

以2-吡啶甲酸为原料,经酯化、缩合、加成合成了平面四齿双核配体3,5-二(2-吡啶基)吡唑。改进合成方法使加成反应的产率由原来的66%提高到98%。     

Ligand‐Directed Divergent Synthesis of Carbo‐ and Heterocyclic Ring Systems

Chemical tools that enable a catalytic reaction to selectively and efficiently yield different products will allow charting of wider chemical space. In ligand‐directed divergent synthesis, a common mode of catalysis is modulated by employing different ligands for catalytic organometallic complexes to transform either common substrates or common reactive intermediates into distinct molecular scaffolds. The strategy has the potential to create important and diverse scaffolds and to unveil novel modes of catalytic transformations for wider synthetic applications. This strategy is described and recent efforts in this emerging field of catalysis, focusing on transition‐metal catalysis for the synthesis of carbo‐ and heterocyclic ring systems, are reviewed.     

一个改进的Dallacker双内酯的合成

以5步反应从邻碘苯甲酸乙酯合成了9,10-二氢-9,9,10,10-双(γ-丁内酯)菲,减少了3步反应,总产率提高7%.又由邻碘苯甲酰氯与乙烷-1,1,2-三羧酸三乙酯缩合,继以消除两个乙酯基合成Dallacker双内酯,反应减少一步,产率则增高13%.还研究了联苯-2,2-二甲酰氯分别与乙烷-1,1,2-三羧酸三乙酯和氰基琥珀酸二乙酯的缩合,均能得到良好的产率.     

5-甲基-2，3-二苯基-1，5-苯并硫氮杂卓-4(5H)-酮的合成

以2-甲硫基苯胺为原料,通过酰化、碘环化以及Suzuki交叉偶联反应,合成了5-甲基-2,3-二苯基-1,5-苯并硫氮杂卓-4(5H)-酮。 分别考察了催化剂对酰化反应、溶剂对碘环化反应的影响,以及催化剂、配体、碱和温度等因素对Suzuki交叉偶联反应的影响,在最佳的反应条件下,反应总收率为68.5%,中间产物和目标产物的结构经IR、NMR和MS等测试技术得以确证。     

Synthesis of 1-aryl indoles via coupling reaction of indoles and aryl halides catalyzed by CuI/metformin

Ullmann-type C–N coupling reaction has been developed for the synthesis of 1-aryl indole derivatives by indoles and aryl halides in the presence of CuI/metformin (CuI/Met) in DMF. This method is very easy, rapid, and high yielding reaction for the synthesis of 1-aryl indoles. In particular, the metformin, which is used as ligand, is inexpensive and nontoxic that is considered to be relatively environmentally benign.     

A novel approach for the synthesis of the peripheral benzodiazepine receptor ligand, PK11195

A new synthesis of the peripheral benzodiazepine receptor ligand, PK11195 has been developed in only six-steps using a Heck-type reaction and a Suzuki coupling to effect the key transformations. The flexibility of this new approach is demonstrated by the synthesis of an iodo-analogue of PK11195 prepared from the corresponding bromide using a copper catalysed aromatic Finkelstein reaction.     

Synthesis of alkoxymethyl derivatives of resorcinarene via the Mannich reaction catalysed with iminodiacetic acid

The conditions of a simple synthesis of tetra(alkoxymethyl) derivatives of resorcinarene via the Mannich reaction catalysed with iminodiacetic acid are described. A possibility of high yield synthesis of such derivatives for the selected straight-chain alcohols is shown. A possible mechanism of this reaction is suggested.     

Calcium carbide as a cost-effective starting material for symmetrical diarylethynes via Pd-catalyzed coupling reaction

A convenient and cost-effective synthetic method for symmetrical diarylethynes from inexpensive calcium carbide and aryl iodide has been developed. The reaction not only proceeds with high yield and selectivity but also tolerates a wide range of functional groups. Application of this reaction has enabled the synthesis of highly functionalized oligo (phenyleneethynylenes) to be accomplished.     

醚基化二茂铁基膦配体的合成及其对钯催化的Suzuki偶联反应的促进作用

通过乙酸1-(2-二苯膦基二茂铁基)-乙基酯和二甘醇反应,制得新的醚基化的二茂铁基膦配体2-二苯膦基二茂铁基-乙基-5-羟基-3-氧杂戊醚(产率77%),其结构经1H NMR、13C NMR、31P NMR及MS鉴定。 初步研究发现,该醚基化的二茂铁基膦可作为支持配体应用于钯催化的Suzuki反应中,可催化溴代芳烃及带吸电子基的氯代芳烃与苯基硼酸偶联反应制得相应的联芳烃。 催化反应数据表明,配体中的醚氧与Pd中心的配位作用对提高该Pd催化剂的催化性能有一定贡献。     

Theoretical insights into enantioselective catalysis: the mechanism of the Kharasch-Sosnovsky reaction

The mechanism of the Kharasch-Sosnovsky reaction has been investigated using B3 LYP/6-31G* calculations on a chiral reaction model [cyclohexene+tert-butyl perbenzoate-->cyclohex-2-enyl benzoate+tert-butyl alcohol, catalyzed by a chiral bisoxazoline-copper(I) complex]. Although two previous reaction mechanisms have been considered, the results are consistent with a new mechanistic pathway. This path involves ligand exchange between the catalyst-cyclohexene complex with tert-butyl perbenzoate to give a catalyst-perester complex, which undergoes an (either one- or two-step) oxidative addition reaction to yield a copper(III) complex. The limiting step of the Kharasch-Sosnovsky reaction consists of an intramolecular step involving the abstraction of an allylic hydrogen from cyclohexene [which is pi-bound to the copper(III) complex]. The resulting allyl-copper(III) complex (subsequent to the loss of tert-butanol) can undergo a haptotropic rearrangement by means of an eta1-allyl/eta3-allyl equilibrium, leading to scrambling between vinylic and allylic positions when an isotopically labeled substrate is used. The allyl-copper(III) ion undergoes a stereospecific reductive elimination involving the pi-bond migration to yield a reaction product-catalyst complex, which can regenerate the alkene-copper(I) complex by ligand exchange. The proposed reaction mechanism is consistent with all known experimental results (including enantioselectivity data).     

Brexane骨架的快速合成策略

本文报道了三环[4,4,0,03,7]壬烷(Brexane)的快速合成策略.该方法以双功能路易斯酸介导的Diels-Alder/碳环化串联反应构建了目标环系,且核心反应具有高度立体选择性,该路线共五步反应,总产率为23％.本工作可为具有该骨架的萜类天然产物的全合成提供一可选的策略.     

New vistas in quinoline synthesis

The gold-catalyzed Friedlander reaction was applied to the condensation of 2-aminoarylketones with β-keto-esters, β-diketones, β-keto-amides, and β-keto-sulfones to afford a diverse range of 2,3,4-trisubstituted quinolines in 3-82% yield. The seven-membered rings 1,3-cycloheptadione and azepane-2,4-dione reacted smoothly in 75% yield. An alternative procedure for the synthesis of 3-(methanesulfonyl)quinolines was developed and provided an entry into late stage manipulation of the 4-position of these quinolines. The requisite 2-aminoarylketones for the Friedlander reaction were prepared in one pot by modified Sugasawa reaction using gallium(III) chloride and boron(III) chloride in 12-54% yield.     

Continuous synthesis for zirconium metal-organic frameworks with high quality and productivity via microdroplet flow reaction

A series of Zr-based metal-organic frameworks were continuously synthesized with high quality and high productivity through microdroplet flow reaction.